a fierce debate-- should the u.s. arm the opposition? i'm erica hill. also tonight, kicking the habit. the president wants to cut oil imports by a third, and some drivers have already gotten the message. hyperactive kids-- why some experts believe artificial food coloring could make the behavior worse. >> mr. president! >> and a bullet meant for president reagan nearly took this man's life. 30 years later james brady is still fighting for gun control. captioning sponsored by cbs from cbs news world headquarters in new york, this is the "cbs evening news" with katie couric. >> hill: good evening. katie is off tonight. just two days ago, libyan rebels seemed ready to move on muammar qaddafi's home town and possibly on tripoli, but tonight, they are on the move in the other direction. their weapons, machine guns for the most part are, no march for qaddafi's heavier weaponry. secretary of state hillary clinton said today no decision has been made about whether to arm the rebels, but there are also reports president obama recently signed a secret order authorizing covert support for them.